Quantitative perturbational molecular orbital calculations for conjugated hydrocarbons

Abstract

Two methods based on Dewar's perturbational molecular orbital approach are shown to be as quantitative for calculation of heats of atomization of conjugated hydrocarbons as the more sophisticated techniques, provided δE_RS is minimized according to Dewar's specification for predicting u.v. spectra. In addition, if this convention is adopted, Dewar's method for deriving the rules governing pericyclic reactions is shown not to be totally equivalent to the Woodward–Hoffman rules, explaining at least one Woodward–Hoffman violation.